Monoclonal autoantibodies recognizing histone variants

Balb/c mice were immunized with affinity purified Ro(SS-A) from human origin in order to allow the preparation of monoclonal anti-Ro(SS-A) antibodies. After fusion of mouse myeloma cells (line Sp2/0 A914) with spleen cells from one of these mice, anti-Ro(SS-A) monoclonals were not obtained, but, instead, two IgM producing hybridomas reactive with histone H1 and one with histone H2B. The specificity of the anti-H1 monoclonals was investigated by means of immunoblotting of very lysine-rich histone variants from mouse which were separated by two-dimensional gelelectrophoresis. One of them (CLB-ANA 105) has H1(0) specificity with respect to the histone variants of mouse and man, but recognizes H5 as well as H1 from Xenopus laevis. Another monoclonal (CLB-ANA 108) reacts with the variant H1c from mouse, exclusively. From the way these monoclonals were produced, we postulate that they were not the result of immunization, but comprise specificities of naturally occurring autoantibodies.